Redirect a page to a node or an external URL

Page#redirect_target resolves the precedence and returns nil for a
destination that is restricted or has no head, so a page with a broken
target renders itself rather than linking nowhere. The banner partial will
call the same method, so the redirect and the link cannot drift.

One hop, no exceptions, checked in publish_draft! rather than as a
validation: two nodes publishing concurrently could each pass a save-time
check and still produce a chain. "Live" means heads only, a draft redirect
that has not published is not yet a link anyone can follow.

Node.search excludes redirecting pages. editor_search does not: an editor
looking for one searches by title, and only the body is worth hiding.

1 files changed, 27 insertions, 0 deletions

diff --git a/app/models/node.rb b/app/models/node.rb
index 6fc6c3dc..52e06d2d 100644
--- a/app/models/node.rb
+++ b/app/models/node.rb
@@ -236,6 +236,32 @@ class Node < ApplicationRecord
       raise ActiveRecord::RecordInvalid.new(self)
     end
 
+    if self.draft.redirect.present?
+      if self.draft.redirect_node_id == self.id
+        errors.add(:base, :redirect_to_self)
+        raise ActiveRecord::RecordInvalid.new(self)
+      end
+
+      if self.draft.redirect_node_id.present?
+        target = Node.find_by(:id => self.draft.redirect_node_id)
+
+        unless target
+          errors.add(:base, :redirect_target_missing)
+          raise ActiveRecord::RecordInvalid.new(self)
+        end
+
+        if target.head&.redirect.present?
+          errors.add(:base, :redirect_to_redirect)
+          raise ActiveRecord::RecordInvalid.new(self)
+        end
+      end
+
+      if Page.redirecting_to(self.id).exists?
+        errors.add(:base, :redirect_would_chain)
+        raise ActiveRecord::RecordInvalid.new(self)
+      end
+    end
+
     path_before = self.unique_name
 
     ActiveRecord::Base.transaction do
@@ -602,6 +628,7 @@ class Node < ApplicationRecord
   def self.search(term, _ = {})
     joins(head: :translations)
       .where("page_translations.search_vector @@ plainto_tsquery('simple', ?)", term)
+      .where(:pages => { :redirect => nil })
       .distinct
   end